PORTLAND, Ore. December 8, 2004. When
Mount St. Helen’s blew its top in 1980, Charlie Crisafulli was 22
years old and just beginning his career as a research ecologist. One of
his first assignments: travel to Mount St. Helens 2 months after the historic
eruption and study the aftermath.

Crisafulli and his colleagues traveled by helicopter into the volcanic
disturbance zones to gather ecological data. Crisafulli, a scientist at
the USDA Forest Service’s Pacific Northwest Research Station, spent
the next 25 years analyzing data that enabled him to produce long-term
data sets to use to study the ecological patterns and processes of species
survival and colonization.
He observed the development of ecological relationships across the volcanic
landscape. Fast forward to October 2, 2004.

“ We flew a boat in by helicopter to Spirit Lake just 2 days before
the October 4, 2004, eruptions to characterize the chemical,
physical, and biological
conditions of the lake,” says Crisafulli. “We surveyed more
than 100 ponds for amphibians and aquatic invertebrates, and live-small
mammals at
14 sites right in front of the crater. Unlike in 1980, when we had very
little pre-eruption data, we now have a broad network of established plots
and lots
of data on hundreds of aquatic and terrestrial species—from microscopic-aquatic
plants, to insects to mammals. This information is important baseline data
for assessing future disturbance from the volcano.”

He says that arriving
on the scene within hours to days after a disturbance event is paramount
for understanding both initial disturbance severity
and long-term biological responses. Of particular importance is documenting
the
types, amounts, and distribution of surviving organisms.

Scientists
learned, explains Crisafulli, that traditional theories of disturbance
and the succession processes were often inadequate for
explaining
ecological
responses to the 1980 eruption of Mount St. Helens. Some of the findings
include:

Disturbance gradients ranged from areas where all life perished,
to zones with nearly complete survival. The eruption involved
several volcanic disturbances—debris
avalanche, lateral blast, mudflows, pyroclastic flow, and tephra-fall—that
interacted with a very diverse pre-eruption landscape to create
a
complex mosaic of disturbance across several hundred square miles.

Chance events, such as timing of a disturbance, greatly determine
the extent of environmental change. The 1980 eruption occurred
on a spring morning.
Had
it happened in late summer and at night, more plants and animals
would have perished. “Events such as the season, and even the time of day,
strongly influence survivorship and recovery,” Crisafulli says. “If
it had been late summer, there would not have been late-lying
patches of snow to protect
subalpine vegetation, or ice covering lakes, which shielded aquatic
organisms from lethal volcanic forces. If it had been at night,
the nocturnal animals
would have been exposed to lethal volcanic forces. Instead, they
had returned to the safety of their subterranean burrows.”

Species
life history characteristics allowed some species populations
to avoid the volcanic impacts by being away from the area. For instance,
some Pacific
salmon and steelhead trout were at sea when the eruption occurred.
When they returned to Mount St. Helens to spawn in the years after the eruption,
stream
conditions had improved. Many migrant songbirds were still on
their winter grounds in Mexico and Central America when the eruption occurred,
and
had
not
yet returned to their summer nesting grounds at Mount St. Helens.

Biological legacies—living and dead—accelerated
recovery. Surviving plants, fungi, and animals were very important
because
they challenged
the theory of the importance of dispersal from distant source
populations that
can prolong or limit colonization. These legacies serve many
ecological functions such as foraging and nesting substrate and
prey and predators,
and facilitated
the colonization of invading species. When survivors were abundant,
complex communities developed rapidly.

Lakes, streams, and forests
responded at different rates after the 1980 eruption. Of key
importance was the extent to which
ecological systems
became nutrient
enriched or impoverished. Lakes became grossly enriched and
responded rapidly. In sharp contrast, terrestrial systems experienced
diminished production
as vegetation was killed and the landscape was covered with nutrient-poor
volcanic
material. Within 6 years of the eruption, most lakes had returned
to conditions typical of the undisturbed Cascade lakes. Whereas, by 2004,
terrestrial systems
had increased productivity, but remained far below that of
a mature forest.

“ Even in areas where all life had perished, small-oasis habitats developed
within a few years of the 1980 eruption,” says Crisafulli. “Plants
became established around small springs that promoted the colonization
of many small mammals, birds, amphibians, and insects. Although embedded
within
a vast,
barren terrain, oases habitats sustained many colonizing organisms,
eliminating the need for dispersal corridors between source populations
and newly created
habitat patches. These oases habitats were of tremendous importance
to the overall biodiversity of the larger landscape, they contributed
much of the
biodiversity.

“
St. Helens has had a very active eruptive past, and if history
provides any indication of future eruptive potential, we may
well expect Mount St. Helens
to cause additional disturbances to the surrounding landscape during
this next century,” Crisafulli explains. “Since 1980,
the volcano has made a great template to study disturbance. More
than 100 physical
and
life scientists
have studied the 1980 eruption and subsequent ecological responses.
And these studies continue to expand our knowledge and long-term
database.”

Crisafulli and his colleagues have a book due to
be published by Springer Verlag in May 2005. Ecological Responses
to the 1980 Eruption
of Mount
St. Helens
is a synthesize of findings from the past two decades. A writers’ workshop, “The
meaning of Mount St. Helens,” is also scheduled to be held
in Portland, Ore., in 2005.